For reprofiling rails of railways, use is generally made of railway vehicles of the type described in the Swiss patent 680,672, equipped with several lapping units which can be, for example, of the type described in the Swiss patents 677973, 678341, 655528 or 666068.
All these reprofiling machines have in common the use of lapping units including a motor, the shaft of which drives in rotation a lapping disk, which disk is brought into contact with the rail for its reprofiling.
Obviously, these lapping disks are subject to wear and must be replaced at regular intervals, generally after several hours of work and this necessitates the stopping of the railway vehicle and the manual intervention of trained operators on each lapping unit. For obvious reasons of cost, the time during which the vehicle stands idle must be limited as much as possible and hence the replacement operation of the lapping disks must be carried out as promptly as possible. Furthermore, to avoid major vibrations of the lapping disks which are rotated at a high speed, their centering must be as accurate as possible.
The driving shafts of the lapping units are usually provided with an adaptor onto which is fastened the lapping disk.
Different modes of fastening are known for lapping disks on the adaptor of a lapping unit, the main ones being:
1. The provision of nuts embedded in the body of the lapping disk when the disk is manufactured, which nuts subsequently cooperate with bolts engaged in through bores of the adaptor of the lapping unit. This mode of fastening suffers numerous drawbacks, in particular it complicates the manufacture of the lapping disks because of the use of bolts and does not allow an accurate centering of the lapping disk. Furthermore, the time required for changing a lapping disk is quite long, since six to eight bolts need to be released and tightened again.
2. The use of segments screwed into the periphery of the lapping disk and protruding from its upper surface, these protrusions being threadably engaged in the periphery of the adaptor. Here also, the centering of the lapping disk cannot be carried out accurately and the time needed for changing the lapping disk is unacceptable. Furthermore, the lapping disk thus fastened cannot be used in totality, since the portion extending between the fastening segments is lost.
3. Also, lapping disks are known which are bonded to an aluminum plate and which can subsequently be fastened by a single central bolt to the adaptor driven by the motor of the lapping unit. Such a mode of fastening is described for example in the U.S. Pat. No. 4,292,768. This system makes possible a rapid fastening and centering of the lapping disk, but its cost is much too high, since for each lapping disk, one has to discard or recover an aluminum plate. Furthermore, the manufacture of these lapping disks is made complicated and expensive because of the use of the aluminum plate employed for their fastening.